U.S. Pat. No. 4,316,996 teaches that 1-hydroxy-2,6-dialkylpiperidines are useful in preventing the discoloration of phenolic antioxidants.
1-Hydroxy-2,2,6,6-tetramethyl-4-acyloxypiperidines and other 1-hydroxy-2,2,6,6-tetramethylpiperidine derivatives are known as effective light stabilizers, but these compounds are not effective as processing stabilizers. They are also structurally distinct from the instant compounds of this invention.
U.S. Pat. Nos. 4,668,721; 4,782,105; 4,876,300 and 4,898,901 describe other hydroxylamines which are useful as processing stabilizers, but these hydroxylamines are structurally quite different from the instant compounds.
H. Kothandraraman et al., J. Poly. Sci. Polymer Letters Ed., 23, 475 (1985) report the preparation of polyacrylamides having the amino group substituted by selected substituted 2,6-diarylpiperidin-4-yl moieties. The instant compounds and their utility as stabilizers are not mentioned or suggested by this scientific article.
The instant 1-hydroxy-2,6-diaryl-4-acyloxypiperidines and 1-hydroxy-2,6-diaryl-4-acylaminopiperidines are novel compounds unknown in the prior art. The precursor amine starting materials are also novel compounds.
The 1-hydroxy-2,6-diaryl-4-acyloxypiperidines and 1-hydroxy-2,6-diaryl-4-acylaminopiperidines of this invention exhibit surprisingly superior properties compared to those of the closest prior art compounds.
The instant compounds are structurally distinct from prior art compounds. Their structures allow for the synthesis of high molecular weight compounds which have low volatility, better compatibility with the substrate and low extractability. The instant compounds provide both melt flow stabilization and good resistance against discoloration during polymer processing. The instant compounds have superior hydrolytic stability over the state of the art phosphite stabilizers and exhibit superior long term heat aging and oxidative induction time over the state of the art hydroxylamine stabilizers.